This section is intended to provide a background or context to the invention that is recited in the claims. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived, implemented or described. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
The following abbreviations are utilized herein:
3GPP third generation partnership project
BS base station
BW bandwidth
CGI cell global identity
DCH dedicated channel
DL downlink (eNB towards UE)
DRX discontinuous reception
eNB E-UTRAN Node B (evolved Node B)
EPC evolved packet core
E-UTRAN evolved UTRAN (LTE)
FACH forward access transport channel
FDMA frequency division multiple access
GSM global system for mobile communication
HO handover or handoff
HSPA high speed packet access
IMEI international mobile equipment identity
IMT-A international mobile telephony-advanced
ITU international telecommunication union
ITU-R ITU radiocommunication sector
LTE long term evolution of UTRAN (E-UTRAN)
LTE-A LTE advanced
MAC medium access control (layer 2, L2)
MM/MME mobility management/mobility management entity
NAS non-access stratum
Node B base station
NW network
OFDMA orthogonal frequency division multiple access
O&M operations and maintenance
PCH paging channel
PCI physical cell identity
PDCP packet data convergence protocol
PHY physical (layer 1, L1)
QoS quality of service
Rel release
RLC radio link control
RNC radio network controller
RRC radio resource control
RRM radio resource management
S-GW serving gateway
SC-FDMA single carrier, frequency division multiple access
UE user equipment, such as a mobile station, mobile node or mobile terminal
UL uplink (UE towards eNB)
UMTS universal mobile telecommunications system
URA UTRAN registration area
UTRAN universal terrestrial radio access network
WI working item
The specification of a communication system known as evolved UTRAN (E-UTRAN, also referred to as UTRAN-LTE or as E-UTRA) is currently nearing completion within the 3GPP. As specified the DL access technique is OFDMA, and the UL access technique is SC-FDMA.
One specification of interest is 3GPP TS 36.300, V8.12.0 (2010-04), “3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Evolved Universal Terrestrial Radio Access (E-UTRA) and Evolved Universal Terrestrial Access Network (E-UTRAN); Overall description; Stage 2 (Release 8),” incorporated by reference herein in its entirety. This system may be referred to for convenience as LTE Rel-8 (which also contains 3G HSPA and its improvements). In general, the set of specifications given generally as 3GPP TS 36.xyz (e.g., 36.211, 36.311, 36.312, etc.) may be seen as describing the Release 8 LTE system. Release 9 versions of these specifications have been published, including 3GPP TS 36.300, V9.7.0 (2011-3), incorporated by reference herein in its entirety. Release 10 versions of these specifications have been published, including 3GPP TS 36.300, V10.4.0 (2011-06), incorporated by reference herein in its entirety.
FIG. 1 reproduces FIG. 4-1 of 3GPP TS 36.300 V8.12.0, and shows the overall architecture of the E-UTRAN system 2 (Rel-8). The E-UTRAN system 2 includes eNBs 3, providing the E-UTRAN user plane (PDCP/RLC/MAC/PHY) and control plane (RRC) protocol terminations towards the UE (not shown). The eNBs 3 are interconnected with each other by means of an X2 interface. The eNBs 3 are also connected by means of an S1 interface to an EPC, more specifically to a MME by means of a S1 MME interface and to a S-GW by means of a S1 interface (MME/S-GW 4). The S1 interface supports a many-to-many relationship between MMEs/S-GWs and eNBs.
The eNB hosts the following functions:                functions for RRM: RRC, Radio Admission Control, Connection Mobility Control, Dynamic allocation of resources to UEs in both UL and DL (scheduling);        IP header compression and encryption of the user data stream;        selection of a MME at UE attachment;        routing of User Plane data towards the EPC (MME/S-GW);        scheduling and transmission of paging messages (originated from the MME);        scheduling and transmission of broadcast information (originated from the MME or O&M); and        a measurement and measurement reporting configuration for mobility and scheduling.        
Of particular interest herein are the further releases of 3GPP LTE (e.g., LTE Rel-10) targeted towards future IMT-A systems, referred to herein for convenience simply as LTE-Advanced (LTE-A). Reference in this regard may be made to 3GPP TR 36.913, V8.0.1 (2009-03), 3rd Generation Partnership Project; Technical Specification Group Radio Access Network; Requirements for Further Advancements for E-UTRA (LTE-Advanced) (Release 8), incorporated by reference herein in its entirety. A goal of LTE-A is to provide significantly enhanced services by means of higher data rates and lower latency with reduced cost. LTE-A is directed toward extending and optimizing the 3GPP LTE Rel-8 radio access technologies to provide higher data rates at very low cost. LTE-A is part of LTE Rel-10. LTE-A is a more optimized radio system fulfilling the ITU-R requirements for IMT-A while maintaining backward compatibility with LTE Rel-8. Reference is further made to a Release 9 version of 3GPP TR 36.913, V9.0.0 (2009-12), incorporated by reference herein in its entirety. Reference is also made to a Release 10 version of 3GPP TR 36.913, V10.0.0 (2011-06), incorporated by reference herein in its entirety.
As is specified in 3GPP TR 36.913, LTE-A should operate in spectrum allocations of different sizes, including wider spectrum allocations than those of Rel-8 LTE (e.g., up to 100 MHz) to achieve the peak data rate of 100 Mbit/s for high mobility and 1 Gbit/s for low mobility. It has been agreed that carrier aggregation is to be considered for LTE-A in order to support bandwidths larger than 20 MHz. Carrier aggregation, where two or more component carriers (CCs) are aggregated, is considered for LTE-A in order to support transmission bandwidths larger than 20 MHz. The carrier aggregation could be contiguous or non-contiguous. This technique, as a bandwidth extension, can provide significant gains in terms of peak data rate and cell throughput as compared to non-aggregated operation as in LTE Rel-8.
A terminal may simultaneously receive one or multiple component carriers depending on its capabilities. A LTE-A terminal with reception capability beyond 20 MHz can simultaneously receive transmissions on multiple component carriers. A LTE Rel-8 terminal can receive transmissions on a single component carrier only, provided that the structure of the component carrier follows the Rel-8 specifications. Moreover, it is required that LTE-A should be backwards compatible with Rel-8 LTE in the sense that a Rel-8 LTE terminal should be operable in the LTE-A system, and that a LTE-A terminal should be operable in a Rel-8 LTE system.
FIG. 1B shows an example of the carrier aggregation, where M Rel-8 component carriers are combined together to form MxRe1-8 BW (e.g., 5×20 MHz=100 MHz given M=5). Rel-8 terminals receive/transmit on one component carrier, whereas LTE-A terminals may receive/transmit on multiple component carriers simultaneously to achieve higher (wider) bandwidths.
UE battery saving has been a big topic in the last few years in UMTS as battery consumption is increasing compared to GSM UEs due to the difference in the supported bands, more complicated functionalities in the UE, and smarter application activities, as non-limiting examples. In the case of UMTS, a UE can be in one of many different states (e.g., Cell-DCH, Cell-FACH, URA/Cell-PCH and IDLE) and the battery consumption is dependent on the state (e.g., different battery consumptions for different states).
In LTE, the network can configure the DRX for RRC CONNECTED UE battery saving so that the UE wakes up only in a limited time. As with UMTS, if the UE does not have activity for a certain time period, the network will release the RRC Connection at some point. From a UE power consumption point of view, a longer DRX and RRC IDLE may be rather similar. However, the network implication will be quite different. In the case of long DRX, as the UE is in the RRC CONNECTED mode, in case the UE is moving and crosses the border of the cell, a handover should be performed. Thus, handover-related measurement signaling and handover signaling will increase. Alternatively, if the UE is in IDLE, RRC Connection Setup signaling will increase but no handover is required. Thus, for fast moving UEs not having constant data activity, the IDLE state is more preferable than long DRX from a network point of view.